Method and system for learning contributions of engine knock background noise for a variable displacement engine

ABSTRACT

Methods and systems are disclosed for operating an engine that includes a knock control system that may determine contributions of individual noise sources to an engine background noise level. The contributions of the individual noise sources may be determined via adjusting timing of a knock window or timing of the individual noise sources.

FIELD

The present application relates to methods and systems for learning andestablishing individual contributions of different engine noise sourcesto an engine knock background noise level of a variable displacementengine.

BACKGROUND/SUMMARY

An engine may include valve actuators for selectively activating anddeactivating cylinders. One or more engine cylinders may be deactivatedwhen less than the engine's full torque capacity is requested so thatengine efficiency may be increased. If one or more cylinders of anengine are deactivated, the remaining cylinders may operate at higherpressures to generate a same amount of torque as compared to if allengine cylinders were operating. Consequently, a propensity for knock tooccur in active engine cylinders may increase when the engine provides arequested amount of torque. Therefore, it may be desirable to include aknock control system with the engine that provides an indication ofdetonation or knock (e.g., ignition of end gases in the cylinder bymeans other than a flame front generated via a spark plug) so thatmitigating actions may be taken.

An engine knock control system may include a knock window for assessingthe presence or absence of engine knock. The knock window is acrankshaft angular interval (e.g., from five crankshaft degrees aftertop dead center compression stroke of the cylinder being assessed forknock to forty-five degrees after top dead center compression stroke ofthe cylinder being assessed for knock) where output of a knock sensor issampled (e.g., measured) via a controller to determine whether or notknock is present in the cylinder. However, if one or more enginecylinders are deactivated, then knock windows associated with thedeactivated cylinders may go unused or may be processed and theirresults may be disregarded. Consequently, controller processing time andresources may be squandered. Further, the deactivation of one or moreengine cylinders may change engine knock background noise levels foractivated cylinders. Consequently, knock may be falsely indicated ormissed in activated cylinders.

The inventors herein have developed an engine operating method,comprising: ceasing to supply fuel to a first engine cylinder via acontroller; reducing a crankshaft duration of a knock window of thefirst engine cylinder from a first duration when the knock window isapplied to evaluate the presence of knock in a cylinder to a secondduration when the knock window is applied to quantify an engine knockbackground noise level; and sampling output of a knock sensor during theknock window via the controller.

By reducing a crankshaft duration of a knock window, it may be possibleto provide the technical result of learning engine knock backgroundnoise levels via shortened knock windows so that noise levels ofspecific engine noise sources may be isolated from noises of otherengine noise sources so that noise levels of the specific noise sourcesmay be properly characterized. Further, instead of adjusting timing of aknock window, it may be possible or desirable to change timing of thespecific noise source so that its noise level may be characterized in adesirable way in the knock window. The noise level of the specific noisesource may then be applied to determine a total or combined enginebackground noise level, which may be the basis for evaluating output ofthe knock sensor to determine the presence or absence of engine knock.

The present description may provide several advantages. In particular,the approach may improve detection of engine knock. Further, theapproach may improve the efficiency at which engine knock backgroundnoise levels may be learned. Further still, the approach may provideways of determining engine knock background noise levels for engineoperating conditions where the engine has not operated or where theengine does not operate frequently.

It should be understood that the summary above is provided to introducein simplified form a selection of concepts that are further described inthe detailed description. It is not meant to identify key or essentialfeatures of the claimed subject matter, the scope of which is defineduniquely by the claims that follow the detailed description.Furthermore, the claimed subject matter is not limited toimplementations that solve any disadvantages noted above or in any partof this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A shows a schematic depiction of an engine system of a vehicle.

FIG. 1B shows example locations for knock sensors for a V8 engine.

FIG. 1C shows an alternative view of knock sensor locations for the V8engine.

FIGS. 2-6 shows a high level flow chart of a way to operate an enginethat includes a knock control system;

FIGS. 7-9 show example engine operating sequences for illustrating themethod of FIGS. 2-6; and

FIG. 10 shows how adjusting timing of noise sources may change engineknock background noise levels.

DETAILED DESCRIPTION

The following description relates to systems and methods for operatingan engine that includes a knock control system. The engine may be of thetype that is shown in FIGS. 1A-1C. The engine may be operated accordingto the method of FIGS. 2-6. The method may learn engine background noiselevels via engine knock windows of deactivated cylinders so that theremay be fewer effects on engine operation. The method may perform asshown in the sequences of FIGS. 7-9. FIG. 10 shows how adjustingactuators may affect engine knock background noise levels.

Turning now to the figures, FIG. 1A depicts an example of a cylinder 14of an internal combustion engine 10, which may be included in a vehicle5. Engine 10 may be controlled at least partially by a control system,including a controller 12, and by input from a human vehicle operator130 via an input device 132. In this example, input device 132 includesan accelerator pedal and a pedal position sensor 134 for generating aproportional pedal position signal. Cylinder (herein, also “combustionchamber”) 14 of engine 10 may include combustion chamber walls 136 witha piston 138 positioned therein. Piston 138 may be coupled to acrankshaft 140 so that reciprocating motion of the piston is translatedinto rotational motion of the crankshaft. Crankshaft 140 may be coupledto at least one vehicle wheel 55 of vehicle 5 via a transmission 54, asfurther described below. Further, a starter motor (not shown) may becoupled to crankshaft 140 via a flywheel to enable a starting operationof engine 10.

In some examples, vehicle 5 may be a hybrid vehicle with multiplesources of torque available to one or more vehicle wheels 55. In otherexamples, vehicle 5 is a conventional vehicle with only an engine or anelectric vehicle with only an electric machine(s). In the example shown,vehicle 5 includes engine 10 and an electric machine 52. Electricmachine 52 may be a motor or a motor/generator. Crankshaft 140 of engine10 and electric machine 52 are connected via transmission 54 to vehiclewheels 55 when one or more clutches 56 are engaged. In the depictedexample, a first clutch 56 is provided between crankshaft 140 andelectric machine 52, and a second clutch 57 is provided between electricmachine 52 and transmission 54. Controller 12 may send a signal to anactuator of each clutch 56 to engage or disengage the clutch, so as toconnect or disconnect crankshaft 140 from electric machine 52 and thecomponents connected thereto, and/or connect or disconnect electricmachine 52 from transmission 54 and the components connected thereto.Transmission 54 may be a gearbox, a planetary gear system, or anothertype of transmission.

The powertrain may be configured in various manners, including as aparallel, a series, or a series-parallel hybrid vehicle. In electricvehicle examples, a system battery 58 may be a traction battery thatdelivers electrical power to electric machine 52 to provide torque tovehicle wheels 55. In some examples, electric machine 52 may also beoperated as a generator to provide electrical power to charge systembattery 58, for example, during a braking operation. It will beappreciated that in other examples, including non-electric vehicleexamples, system battery 58 may be a typical starting, lighting,ignition (SLI) battery coupled to an alternator 46.

Alternator 46 may be configured to charge system battery 58 using enginetorque via crankshaft 140 during engine running. In addition, alternator46 may power one or more electrical systems of the engine, such as oneor more auxiliary systems including a heating, ventilation, and airconditioning (HVAC) system, vehicle lights, an on-board entertainmentsystem, and other auxiliary systems based on their correspondingelectrical demands. In one example, a current drawn on the alternatormay continually vary based on each of an operator cabin cooling demand,a battery charging requirement, other auxiliary vehicle system demands,and motor torque. A voltage regulator may be coupled to alternator 46 inorder to regulate the power output of the alternator based upon systemusage requirements, including auxiliary system demands.

Cylinder 14 of engine 10 can receive intake air via a series of intakepassages 142 and 144 and an intake manifold 146. Intake manifold 146 cancommunicate with other cylinders of engine 10 in addition to cylinder14. One or more of the intake passages may include one or more boostingdevices, such as a turbocharger or a supercharger. For example, FIG. 1Ashows engine 10 configured with a turbocharger, including a compressor174 arranged between intake passages 142 and 144 and an exhaust turbine176 arranged along an exhaust passage 135. Compressor 174 may be atleast partially powered by exhaust turbine 176 via a shaft 180 when theboosting device is configured as a turbocharger. However, in otherexamples, such as when engine 10 is provided with a supercharger,compressor 174 may be powered by mechanical input from a motor or theengine and exhaust turbine 176 may be optionally omitted. In still otherexamples, engine 10 may be provided with an electric supercharger (e.g.,an “eBooster”), and compressor 174 may be driven by an electric motor.In still other examples, engine 10 may not be provided with a boostingdevice, such as when engine 10 is a naturally aspirated engine.

A throttle 162 including a throttle plate 164 may be provided in theengine intake passages for varying a flow rate and/or pressure of intakeair provided to the engine cylinders. For example, throttle 162 may bepositioned downstream of compressor 174, as shown in FIG. 1A, or may bealternatively provided upstream of compressor 174. A position ofthrottle 162 may be communicated to controller 12 via a signal from athrottle position sensor.

An exhaust manifold 148 can receive exhaust gases from other cylindersof engine 10 in addition to cylinder 14. An exhaust gas sensor 126 isshown coupled to exhaust manifold 148 upstream of an emission controldevice 178. Exhaust gas sensor 126 may be selected from among varioussuitable sensors for providing an indication of an exhaust gas air/fuelratio (AFR), such as a linear oxygen sensor or UEGO (universal orwide-range exhaust gas oxygen), a two-state oxygen sensor or EGO, a HEGO(heated EGO), a NOx, a HC, or a CO sensor, for example. In the exampleof FIG. 1A, exhaust gas sensor 126 is a UEGO sensor. Emission controldevice 178 may be a three-way catalyst, a NOx trap, various otheremission control devices, or combinations thereof. In the example ofFIG. 1A, emission control device 178 is a three-way catalyst.

Each cylinder of engine 10 may include one or more intake valves and oneor more exhaust valves. For example, cylinder 14 is shown including atleast one intake poppet valve 150 and at least one exhaust poppet valve156 located at an upper region of cylinder 14. In some examples, eachcylinder of engine 10, including cylinder 14, may include at least twointake poppet valves and at least two exhaust poppet valves located atan upper region of the cylinder. In this example, intake valve 150 maybe controlled by controller 12 by cam actuation via cam actuation system152, including one or more cams 151. Similarly, exhaust valve 156 may becontrolled by controller 12 via cam actuation system 154, including oneor more cams 153. The position of intake valve 150 and exhaust valve 156may be determined by valve position sensors (not shown) and/or camshaftposition sensors 155 and 157, respectively.

During some conditions, controller 12 may vary the signals provided tocam actuation systems 152 and 154 to control the opening and closing ofthe respective intake and exhaust valves. The intake and exhaust valvetiming may be controlled concurrently, or any of a possibility ofvariable intake cam timing, variable exhaust cam timing, dualindependent variable cam timing, or fixed cam timing may be used. Eachcam actuation system may include one or more cams and may utilize one ormore of variable displacement engine (VDE), cam profile switching (CPS),variable cam timing (VCT), variable valve timing (VVT), and/or variablevalve lift (VVL) systems that may be operated by controller 12 to varyvalve operation. In alternative examples, intake valve 150 and/orexhaust valve 156 may be controlled by electric valve actuation. Forexample, cylinder 14 may alternatively include an intake valvecontrolled via electric valve actuation and an exhaust valve controlledvia cam actuation, including CPS and/or VCT systems. In other examples,the intake and exhaust valves may be controlled by a common valveactuator (or actuation system) or a variable valve timing actuator (oractuation system).

As further described herein, intake valve 150 and exhaust valve 156 maybe deactivated during VDE mode via electrically actuated rocker armmechanisms. In another example, intake valve 150 and exhaust valve 156may be deactivated via a CPS mechanism in which a cam lobe with no liftis used for deactivated valves. Still other valve deactivationmechanisms may also be used, such as for electrically actuated valves.In one example, deactivation of intake valve 150 may be controlled by afirst VDE actuator (e.g., a first electrically actuated rocker armmechanism, coupled to intake valve 150) while deactivation of exhaustvalve 156 may be controlled by a second VDE actuator (e.g., a secondelectrically actuated rocker arm mechanism, coupled to exhaust valve156). In alternate examples, a single VDE actuator may controldeactivation of both intake and exhaust valves of the cylinder. In stillother examples, a single cylinder valve actuator deactivates a pluralityof cylinders (both intake and exhaust valves), such as all of thecylinders in an engine bank, or a distinct actuator may controldeactivation for all of the intake valves while another distinctactuator controls deactivation for all of the exhaust valves of thedeactivated cylinders. It will be appreciated that if the cylinder is anon-deactivatable cylinder of the VDE engine, then the cylinder may nothave any valve deactivating actuators. Each engine cylinder may includethe valve control mechanisms described herein. Intake and exhaust valvesare held in closed positions over one or more engine cycles whendeactivated so as to prevent flow into or out of cylinder 14.

Cylinder 14 can have a compression ratio, which is a ratio of volumeswhen piston 138 is at bottom dead center (BDC) to top dead center (TDC).In one example, the compression ratio is in the range of 9:1 to 10:1.However, in some examples where different fuels are used, thecompression ratio may be increased. This may happen, for example, whenhigher octane fuels or fuels with a higher latent enthalpy ofvaporization are used. The compression ratio may also be increased ifdirect injection is used due to its effect on engine knock.

Each cylinder of engine 10 may include a spark plug 192 for initiatingcombustion. An ignition system 190 can provide an ignition spark tocombustion chamber 14 via spark plug 192 in response to a spark advancesignal from controller 12, under select operating modes. Spark timingmay be adjusted based on engine operating conditions and driver torquedemand. For example, spark may be provided at minimum spark advance forbest torque (MBT) timing to maximize engine power and efficiency.Controller 12 may input engine operating conditions, including enginespeed, engine load, and exhaust gas AFR, into a look-up table and outputthe corresponding MBT timing for the input engine operating conditions.In other examples, spark may be retarded from MBT, such as to expeditecatalyst warm-up during engine start or to reduce an occurrence ofengine knock.

In some examples, each cylinder of engine 10 may be configured with oneor more fuel injectors for providing fuel thereto. As a non-limitingexample, cylinder 14 is shown including a direct fuel injector 166 and aport fuel injector 66. Fuel injectors 166 and 66 may be configured todeliver fuel received from a fuel system 8. Fuel system 8 may includeone or more fuel tanks, fuel pumps, and fuel rails. Fuel injector 166 isshown coupled directly to cylinder 14 for injecting fuel directlytherein in proportion to a pulse width of a signal received fromcontroller 12. Port fuel injector 66 may be controlled by controller 12in a similar way. In this manner, fuel injector 166 provides what isknown as direct injection (hereafter also referred to as “DI”) of fuelinto cylinder 14. While FIG. 1A shows fuel injector 166 positioned toone side of cylinder 14, fuel injector 166 may alternatively be locatedoverhead of the piston, such as near the position of spark plug 192.Such a position may increase mixing and combustion when operating theengine with an alcohol-based fuel due to the lower volatility of somealcohol-based fuels. Alternatively, the injector may be located overheadand near the intake valve to increase mixing. Fuel may be delivered tofuel injectors 166 and 66 from a fuel tank of fuel system 8 via fuelpumps and fuel rails. Further, the fuel tank may have a pressuretransducer providing a signal to controller 12.

Fuel injectors 166 and 66 may be configured to receive different fuelsfrom fuel system 8 in varying relative amounts as a fuel mixture andfurther configured to inject this fuel mixture directly into cylinder.For example, fuel injector 166 may receive alcohol fuel and fuelinjector 66 may receive gasoline. Further, fuel may be delivered tocylinder 14 during different strokes of a single cycle of the cylinder.For example, directly injected fuel may be delivered at least partiallyduring a previous exhaust stroke, during an intake stroke, and/or duringa compression stroke. Port injected fuel may be injected after intakevalve closing of a previous cycle of the cylinder receiving fuel and upuntil intake valve closing of the present cylinder cycle. As such, for asingle combustion event (e.g., combustion of fuel in the cylinder viaspark ignition), one or multiple injections of fuel may be performed percycle via either or both injectors. The multiple DI injections may beperformed during the compression stroke, intake stroke, or anyappropriate combination thereof in what is referred to as split fuelinjection.

Fuel tanks in fuel system 8 may hold fuels of different fuel types, suchas fuels with different fuel qualities and different fuel compositions.The differences may include different alcohol content, different watercontent, different octane, different heats of vaporization, differentfuel blends, and/or combinations thereof, etc. One example of fuels withdifferent heats of vaporization includes gasoline as a first fuel typewith a lower heat of vaporization and ethanol as a second fuel type witha greater heat of vaporization. In another example, the engine may usegasoline as a first fuel type and an alcohol-containing fuel blend, suchas E85 (which is approximately 85% ethanol and 15% gasoline) or M85(which is approximately 85% methanol and 15% gasoline), as a second fueltype. Other feasible substances include water, methanol, a mixture ofalcohol and water, a mixture of water and methanol, a mixture ofalcohols, etc. In still another example, both fuels may be alcoholblends with varying alcohol compositions, wherein the first fuel typemay be a gasoline alcohol blend with a lower concentration of alcohol,such as Eli) (which is approximately 10% ethanol), while the second fueltype may be a gasoline alcohol blend with a greater concentration ofalcohol, such as E85 (which is approximately 85% ethanol). Additionally,the first and second fuels may also differ in other fuel qualities, suchas a difference in temperature, viscosity, octane number, etc. Moreover,fuel characteristics of one or both fuel tanks may vary frequently, forexample, due to day to day variations in tank refilling.

Controller 12 is shown in FIG. 1A as a microcomputer, including amicroprocessor unit 106, input/output ports 108, an electronic storagemedium for executable programs (e.g., executable instructions) andcalibration values shown as non-transitory read-only memory chip 110 inthis particular example, random access memory 112, keep alive memory114, and a data bus. Controller 12 may receive various signals fromsensors coupled to engine 10, including signals previously discussed andadditionally including a measurement of inducted mass air flow (MAF)from a mass air flow sensor 122; an engine coolant temperature (ECT)from a temperature sensor 116 coupled to a cooling sleeve 118; anexhaust gas temperature from a temperature sensor 158 coupled to exhaustpassage 135; a crankshaft position signal from a Hall effect sensor 120(or other type) coupled to crankshaft 140; throttle position from athrottle position sensor 163; signal UEGO from exhaust gas sensor 126,which may be used by controller 12 to determine the air-fuel ratio ofthe exhaust gas; engine vibrations (e.g., caused by knock) via vibrationsensing knock sensor 90; and an absolute manifold pressure signal (MAP)from a MAP sensor 124. An engine speed signal, RPM, may be generated bycontroller 12 from crankshaft position. The manifold pressure signal MAPfrom MAP sensor 124 may be used to provide an indication of vacuum orpressure in the intake manifold. Controller 12 may infer an enginetemperature based on the engine coolant temperature and infer atemperature of emission control device 178 based on the signal receivedfrom temperature sensor 158.

Controller 12 receives signals from the various sensors of FIG. 1A andemploys the various actuators of FIG. 1A to adjust engine operationbased on the received signals and instructions stored on a memory of thecontroller. For example, the controller may transition the engine tooperating in VDE mode by actuating valve actuators 152 and 154 todeactivate selected cylinders, as further described with respect to FIG.5.

As described above, FIG. 1A shows only one cylinder of a multi-cylinderengine. As such, each cylinder may similarly include its own set ofintake/exhaust valves, fuel injector(s), spark plug, etc. It will beappreciated that engine 10 may include any suitable number of cylinders,including 2, 3, 4, 5, 6, 8, 10, 12, or more cylinders. Further, each ofthese cylinders can include some or all of the various componentsdescribed and depicted by FIG. 1A with reference to cylinder 14.

During selected conditions, such as when the full torque capability ofengine 10 is not requested, one of a first or a second cylinder groupmay be selected for deactivation by controller 12 (herein also referredto as a VDE mode of operation). During the VDE mode, cylinders of theselected group of cylinders may be deactivated by shutting offrespective fuel injectors 166 and 66. Further, valves 150 and 156 may bedeactivated and held closed over one or more engine cycles. While fuelinjectors of the disabled cylinders are turned off, the remainingenabled cylinders continue to carry out combustion, with correspondingfuel injectors and intake and exhaust valves active and operating. Tomeet torque requirements, the controller adjusts the amount of airentering active engine cylinders. Thus, to provide equivalent enginetorque that an eight cylinder engine produces at 0.2 engine load and aparticular engine speed, the active engine cylinders may operate athigher pressures than engine cylinders when the engine is operated withall engine cylinders being active. This requires higher manifoldpressures, resulting in lowered pumping losses and increased engineefficiency. Additionally, the lower effective surface area (from onlythe active cylinders) exposed to combustion reduces engine heat losses,increasing the thermal efficiency of the engine.

Referring now to FIG. 1B, a plan view of engine 10 is shown. Front 10 aof engine 10 may include a front end accessory drive (FEAD) (not shown)to provide power to an alternator, power steering system, and airconditioning compressor. In this example, engine 10 is shown in a V8configuration with eight cylinders that are numbered 1-8. Engine knockmay be sensed via four knock sensors 90 a-90 d. The knock sensors arepositioned in the valley of engine block 9. In this example, output ofknock sensor 90 a is sampled via controller 12 during the knock windows(e.g., crankshaft angular intervals) of engine cylinders one and two.Thus, knock sensor 90 a is associated with cylinders one and two.However, if knock sensor 90 a (the primary knock sensor of cylindernumbers one and two) is suspected of being degraded, output of knocksensor 90 b (the secondary knock sensor of cylinder numbers one and two)may be sampled or measured in knock windows associated with enginecylinder numbers one and two. Output of knock sensor 90 b is sampled viacontroller 12 during the knock windows of engine cylinders three andfour. However, if knock sensor 90 b (the primary knock sensor ofcylinder numbers three and four) is suspected of being degraded, outputof knock sensor 90 a (the secondary knock sensor of cylinder numbersthree and four) may be sampled or measured in knock windows associatedwith engine cylinder numbers three and four. Thus, knock sensor 90 b isassociated with cylinders three and four. Output of knock sensor 90 c issampled via controller 12 during the knock windows of engine cylindersfive and six. Thus, knock sensor 90 c is associated with cylinders fiveand six. However, if knock sensor 90 c (the primary knock sensor ofcylinder numbers five and six) is suspected of being degraded, output ofknock sensor 90 d (the secondary knock sensor of cylinder numbers fiveand six) may be sampled or measured in knock windows associated withengine cylinder numbers five and six. Output of knock sensor 90 d issampled via controller 12 during the knock windows of engine cylinders 7and 8. Thus, knock sensor 90 d is associated with cylinders seven andeight. However, if knock sensor 90 d (the primary knock sensor ofcylinder numbers seven and eight) is suspected of being degraded, outputof knock sensor 90 c (the secondary knock sensor of cylinder numbersseven and eight) may be sampled or measured in knock windows associatedwith engine cylinder numbers seven and eight. The plurality of knocksensors improves the ability to detect knock for each cylinder sinceattenuation of engine vibrations from knock increases as the distancefrom the knocking cylinder to the knock sensor increases. Knock sensoroutput is not sampled when the knock windows are closed.

Referring now to FIG. 1C, a front view of engine 10 is shown. Engineblock 9 includes a valley 10 b where engine knock sensors 90 a and 90 care mounted to block 9. By mounting knock sensors 90 a and 90 c in thevalley 10 b, a good signal to noise ratio may be available so that knockmay be more reliably detected. However, the mounting locations of knocksensors 90 a-90 d may also allow some fuel injector control actions tobe observed by some sensors and not by others. Thus, background noiselevels of some cylinders may be higher or lower than other cylinders.Additionally, the distance of a fuel injector that opens or closes neara knock window of another engine cylinder may affect an amount of timethat it takes for a vibration to travel from the operating fuel injectorto the knock sensor. And, a longer time for the vibration to travel fromthe fuel injector to the knock sensor may allow the vibration to enter aknock window for a cylinder. As such, knock sensor location, firingorder, and engine configuration may also affect engine knock backgroundnoise levels for some engine cylinders.

Thus, the system of FIGS. 1A-1C provides for a system for operating anengine, comprising: a variable displacement engine including at leastone vibration sensing engine knock sensor; and a controller includingexecutable instructions stored in non-transitory memory to retard sparktiming of an engine cylinder, adjust timing of an actuator, and samplethe at least one vibration sensing engine knock sensor during a knockwindow of the engine cylinder in response to a request to learn anengine knock background noise level. The system includes where theengine knock background noise level is an engine knock base backgroundnoise level that does not include noise generated via the actuatorclosing while the knock window is open. The system includes where theactuator is a fuel injector or a poppet valve. The system furthercomprises additional instructions to determine a presence or absence ofknock in the engine cylinder via the engine knock background noiselevel. The system further comprises additional instructions to integratethe samples of the at least one vibration sensing engine knock sensorduring the knock window.

Referring now to FIGS. 2-6, a method for operating an engine is shown.The method of FIGS. 2-6 may be included in and may cooperate with thesystem of FIGS. 1A-1C. At least portions of method 200 may beincorporated in the system of FIGS. 1A-1C as executable instructionsstored in non-transitory memory. In addition, other portions of method200 may be performed via a controller transforming operating states ofdevices and actuators in the physical world. The controller may employengine actuators of the engine system to adjust engine operation.Further, method 200 may determine selected control parameters fromsensor inputs. The engine may be rotating while method 200 is performed.The method of FIGS. 2-6 may provide the sequences of FIGS. 7-9.

At 202, method 200 determines vehicle and engine operating conditionsvia the sensors described in FIGS. 1A-1C. Method 200 may determineoperating conditions including but not limited to engine speed, engineload, engine temperature, ambient temperature, fuel injection timing,knock sensor output, fuel type, fuel octane, engine position, and engineair flow. Method 200 proceeds to 204.

At 204, method 200 judges if conditions are met for enteringdeceleration cylinder cutout (DCCO). During DCCO, fuel delivery to theengine is ceased and intake and exhaust poppet valves of the engine areclosed and held closed for at least an engine cycle (e.g., twocrankshaft revolutions). By ceasing fuel delivery to the cylinders,engine fuel consumption may be reduced. In addition, closing the intakeand exhaust poppet valves prevents air from being pumped through theengine and upsetting a chemical balance in the catalyst. In one example,method 200 may judge that the engine may enter DCCO when driver demandtorque is less than a threshold torque and when vehicle speed is greaterthan a threshold vehicle speed. However, the engine may enter DCCOduring other vehicle operating conditions. Further, other conditions mayhave to be met to enter DCCO mode. For example, engine coolanttemperature may have to be greater than a predetermined temperature toenter DCCO mode. If method 200 judges that conditions are met forentering DCCO mode, the answer is yes and method 200 proceeds to 220.DCCO mode may be requested when the answer is yes. Otherwise, the answeris no and method 200 proceeds to 206.

At 206, method 200 judges if conditions are met for enteringdeceleration fuel shut off (DFSO). During DFSO, fuel delivery to theengine is ceased and intake and exhaust poppet valves of the enginecontinue to open and close as the engine rotates. By ceasing fueldelivery to the cylinders, engine fuel consumption may be reduced. Inaddition, allowing the intake and exhaust valves to continue to open andclose allows pressure to be maintained in engine cylinders to lowerengine oil consumption. In one example, method 200 may judge that theengine may enter DFSO when driver demand torque is less than a thresholdtorque and when vehicle speed is greater than a threshold vehicle speed.However, the engine may enter DFSO during other vehicle operatingconditions. Further, other conditions may have to be met to enter DFSOmode. For example, engine coolant temperature may have to be greaterthan a predetermined temperature to enter DFSO mode. If method 200judges that conditions are met for entering DFSO mode, the answer is yesand method 200 proceeds to 240. DFSO mode may be requested when theanswer is yes. Otherwise, the answer is no and method 200 proceeds to208.

At 208, method 200 judges if conditions are met for entering a variabledisplacement mode where the engine is operated with fewer than all ofits cylinders. For example, the engine may operate in a VDE mode wherethe number of activated cylinders (e.g., cylinders that are combustingfuel) is adjusted according to or based on a driver demand torque andengine speed. Further, the cylinders that are active may be a same groupof cylinders (e.g., 1-4-6-7) that does not change when engaged in aparticular variable displacement engine (VDE) mode while engine speedand load are constant, which may be referred to as stationary VDE mode.Alternatively, the cylinders that are active may be a group of cylindersin which the cylinder numbers change from engine cycle to engine cyclewhen engine speed and load are constant (e.g., cylinders 1-4-6-7 duringa first engine cycle and cylinders 2-4-5-8 during a second enginecycle), which may be referred to as rolling VDE. In one example, method200 may judge that the engine may enter a VDE mode when driver demandtorque is within a prescribed range and engine speed is within aprescribed range. Further, other conditions may have to be met to enterVDE mode. For example, engine coolant temperature may have to be greaterthan a predetermined temperature. If method 200 judges that conditionsare met for entering VDE mode, the answer is yes and method 200 proceedsto 260. VDE mode may be requested when the answer is yes. Otherwise, theanswer is no and method 200 proceeds to 210.

At 210, method 200 judges if conditions are met for entering an engineknock control mode where the engine may operate with a small amount ofengine knock to improve efficiency and where the level of engine knockis controlled to reduce the possibility of engine component degradation.In one example, method 200 may judge that the engine may enter theengine knock control mode when engine temperature is greater than athreshold temperature and engine load is greater than a threshold engineload. If method 200 judges that conditions are met for entering anengine knock control mode, the answer is yes and method 200 proceeds to212. The engine knock control mode may be requested when the answer isyes. Otherwise, the answer is no and method 200 proceeds to 280.

At 212, method 200 assesses whether or not knock should be indicated forthe selected cylinder that is being evaluated for engine knock (e.g.,cylinder j). FIG. 7 shows operation of the engine and controllerincluding knock windows and knock sensor sampling (e.g., measuring)according to the method of FIG. 2 for detecting knock when engine knockbackground noise levels are not being determined. In one example, method200 computes a knock intensity value for cylinder j by integratingsampled output of the knock sensor during the open knock window ofcylinder j and divides the integrated knock sensor output by the totalengine knock background noise level of cylinder j for the present enginespeed and engine load (e.g., Cyl_combined_noise (j)).

The total or combined engine knock background noise level may beexpressed as: Cyl_combined_noise (j)=Cyl_base_noise (j)+Cyl_inj_noise(j)+Cyl_vlv_noise (j), where Cyl_combined_noise (j) is the total engineknock background noise for cylinder j, Cyl_base_noise (j) is the engineknock base background noise for cylinder j, Cyl_inj_noise (j) is thefuel injector noise that is present in the knock window of cylinder j,and Cyl_vlv_noise (j) is the poppet valve noise present in the knockwindow of cylinder (j). Accordingly, any one of the variables in thecombined background noise equation may be solved knowing three of theother variables. For example, Cyl_base_noise (j)=Cyl_combined_noise(j)−Cyl_inj_noise (j)−Cyl_vlv_noise (j).

The total engine knock background noise level may be retrieved fromcontroller memory or it may be determined from individual noisecontributions that have been retrieved from memory as previouslyindicated. If knock is detected, the spark is retarded for cylinder jand then the spark timing is advanced back toward the MBT (minimum sparkadvance for best engine torque at the present engine speed and load)spark timing for cylinder j. For example, if the knock intensity valuefor cylinder number one exceeds a threshold level, then knock isindicated for cylinder number one and spark timing of cylinder numberone is retarded by five crankshaft degrees. The spark timing forcylinder number one may be advanced by five crankshaft degrees withinten seconds of when the spark timing of cylinder number one was retardedbased on knock. If knock is not indicated, spark timing for the cylinderremains at its requested or base timing (e.g., knock limited sparktiming or MBT timing). The presence or absence of engine knock for eachcylinder may be determined in this way. The cylinder number j may beadjusted according to an engine firing order each engine cycle (e.g.,two revolutions) so that knock is evaluated for each engine cylindereach engine cycle. Method 200 proceeds to exit after adjusting enginespark timing in cylinder j for engine knock.

At 220, method 200 deactivates fuel flow to the engine cylinders whilethe engine crankshaft continues to rotate. The engine may continue torotate via the vehicle's kinetic energy rotating the engine via thevehicle's wheels. Fuel flow to the engine may be deactivated by closingall fuel injectors of the engine. Method 200 proceeds to 222.

At 222, method 200 closes and holds closed all engine intake and exhaustpoppet valves for at least an engine cycle while the engine crankshaftcontinues to rotate. The intake and exhaust valves may be held closedvia a variable valve actuator system. By closing the intake and exhaustvalves, air flow to the catalyst may be reduced to improve engineemissions. Method 200 proceeds to 224.

At 224, method 200 judges if it is desirable to learn engine knock basebackground noise levels at the present engine speed. Method 200 mayjudge that it is desirable to learn engine knock base background noiselevels at the present engine speed if engine knock indication levels aregreater or less than is expected for the present engine speed. Further,method 200 may judge that it is desirable to learn engine knock basebackground noise levels at the present engine speed if engine knock basebackground noise levels have not been determined for a predeterminedamount of time or a predetermined distanced traveled by the vehicle. Ifmethod 200 judges that it is desirable to learn engine knock basebackground noise levels at the present engine speed, the answer is yesand method 200 proceeds to 226. Learning engine knock base backgroundnoise levels may be requested when the answer is yes. If method 200judges that it is not desirable to learn engine knock base backgroundnoise levels at the present engine speed, then the answer is no andmethod 200 proceeds to 234.

At 226, method 200 determines engine knock base background noise levelsfor engine cylinders. In one example, method 200 selects a cylinder(e.g., cylinder j, where j is a number assigned to a cylinder and wherethe value of j may be adjusted to learn engine knock background noiselevels for all engine cylinders) and integrates output of a knock sensorduring a portion of the open knock window of the selected cylinder. Theoutput of the knock sensor may be integrated numerically or via anintegrator circuit to determine the base background noise level of theselected cylinder. The engine knock base background noise level mayinclude noise from the crankshaft, camshaft, and front end accessories,but it does not include noise form injectors opening and/or closing orpoppet valves opening and/or closing during the open knock window of theselected cylinder. Method 200 proceeds to 228.

At 228, method 200 judges if engine knock base background noise levelsat the present engine speed have been determined for all enginecylinders. Method 200 may keep a record of which engine knock basebackground noise levels have been updated for particular engine speedsand loads. If method 200 judges that engine knock base background noiselevels at the present engine speed have been determined for all enginecylinders, then the answer is yes and method 200 proceeds to 230.Otherwise, the answer is no and method 200 proceeds to 229.

At 229, method 200 selects a new engine cylinder for leaning andevaluating the engine knock base background noise level. A unique engineknock base background noise level may be determined for each enginecylinder at selected engine speeds and loads. Further, unique engineknock base background noise levels for each engine operating mode,engine speed, and engine load may be determined. However, since theengine is operating in DCCO mode at zero cylinder load, the values ofall engine knock base background noise levels are not determined at 226.Method 200 may select a new cylinder to evaluate for engine knock basebackground noise levels via incrementing, decrementing, or otherwiseadjusting the value of j. Method 200 returns to 226 after selecting anew engine cylinder to learn and evaluate engine knock base backgroundnoise levels.

At 230, method 200 judges if all engine knock base background noiselevels determined at 226 are within a threshold value of an averagevalue of the engine knock base background noise levels determined at226. For example, if the engine knock background noise levels determinedat 226 are 1.1, 1.05, 1.08, and 1.15 for a four cylinder engine, whichaverages to 1.095, and the threshold value is 0.05, which produces arange between 1.045 and 1.145, then the answer is yes and method 200proceeds to 231. However, if the threshold value is 0.02, then theanswer is no and method 200 proceeds to 232.

At 232, method 200 requests diagnostics for the knock sensor of theselected cylinder that has a higher or lower engine knock basebackground noise than is expected (e.g., cylinders that exhibit engineknock base background noise levels that are greater or less than theaverage value determined at 230 plus or minus the threshold valuedescribed at 230). The threshold value may be empirically determined viarotating the engine with a dynamometer and recording engine knock basebackground noise levels for the engine cylinders. The diagnostic mayinclude applying a voltage to the knock sensor or causing a cylinder toknock and monitoring knock sensor output to determine whether or not theknock sensor is performing as expected. Method 200 proceeds to 234.

At 231, method 200 stores engine knock base background noise levelsdetermined at 226 to controller memory. The engine knock base backgroundnoise levels stored to controller memory may be retrieved from memory todetermine the presence or absence of engine knock when combustion isresumed in the engine and the engine is operating at a speed near thepresent engine speed at which engine knock base background noise levelswere determined. For example, if engine knock base background noiselevels were determined at an engine speed of 2000 RPM, then the engineknock base background noise levels may be applied to determine thecombined engine knock background noise levels for the engine cylinderswhen the engine is combusting fuel at 2000 RPM at engine loads between0.07 and 1. By learning engine knock base background noise levels whenthe engine is not operating (e.g., combusting fuel), it may be possibleto learn fewer engine knock base background noise levels. In particular,the engine knock base background noise levels determined when the enginewas in DCCO mode may be applied when the engine is combusting fuel inall cylinders or in VDE modes so that engine operation while the engineis running may not have to be changed to determine engine knock basebackground noise levels. Method 200 proceeds to 234.

At 234, method 200 judges if vehicle operating conditions are present toexit DCCO mode. In one example, the engine may exit DCCO mode whendriver demand torque exceeds a threshold level. The engine may also exitDCCO mode when driver demand torque exceeds a threshold torque evenbefore all the instructions of FIG. 3 are completed. If method 200judges that conditions are present to exit DCCO mode, then the answer isyes and method 200 proceeds to 206. Otherwise, the answer is no andmethod 200 returns to 224.

At 240, method 200 deactivates fuel flow to the engine cylinders whilethe engine crankshaft continues to rotate. The engine may continue torotate via the vehicle's kinetic energy rotating the engine via thevehicle's wheels. Fuel flow to the engine may be deactivated by closingall fuel injectors of the engine. Method 200 proceeds to 242.

At 242, method 200 continues to open and close all engine intake andexhaust poppet valves while the engine crankshaft continues to rotate.By operating the intake and exhaust valves, pressure in the enginecylinders may be maintained at a level where engine oil consumption maybe reduced. Method 200 proceeds to 244.

At 244, method 200 judges if it is desirable to learn engine knock basebackground noise levels at the present engine speed. Method 200 mayjudge that it is desirable to learn engine knock base and/or valvebackground noise levels at the present engine speed if engine knockindication levels are greater or less than is expected for the presentengine speed. In addition, method 200 may judge that it is desirable tolearn engine knock background noise levels at the present engine speedif engine knock background noise levels have not been determined for apredetermined amount of time or a predetermined distanced traveled bythe vehicle. If method 200 judges that it is desirable to learn engineknock background noise levels at the present engine speed, the answer isyes and method 200 proceeds to 246. Learning engine knock backgroundnoise levels may be requested when the answer is yes. If method 200judges that it is not desirable to learn engine knock background noiselevels at the present engine speed, then the answer is no and method 200proceeds to 254.

At 246, method 200 determines engine knock base background noise levelsand engine knock valve background noise levels for engine cylinders. Inone example, method 200 selects a cylinder (e.g., cylinder j, where j isa number assigned to a cylinder and where the value of j may be adjustedto learn engine knock background noise levels for all engine cylinders)and integrates output of a knock sensor during a portion of the openknock window of the selected cylinder when timing of intake and exhaustpoppet valves is adjusted so that the intake and exhaust valves do notopen or close when engine cylinder knock windows are open (e.g.,predetermined crankshaft angular intervals where output of one or moreknock sensors is sampled via the controller). The output of the knocksensor may be integrated numerically or via an integrator circuit todetermine the base background noise level of the selected cylinder. Theengine knock base background noise level may include noise from thecrankshaft, camshaft, and front end accessories, but it does not includenoise form injectors opening and/or closing or poppet valves openingand/or closing during the open knock window of the selected cylinder.

Method 200 also determines engine knock valve noise levels for theengine cylinders by adjusting timing of intake and exhaust poppet valvesso that the intake and exhaust valves open and/or close when cylinderknock windows are open. For example, method 200 may advance timing ofintake or exhaust poppet valves of cylinder number one to determinevalve noise for cylinder number three in an eight cylinder engine havinga firing order of 1-3-7-2-6-5-4-8. Once intake and/or exhaust valvetiming is adjusted such that the intake and/or poppet valves closeduring an open knock window, then method 200 integrates output of aknock sensor during a portion of the open knock window of the selectedcylinder when timing of intake and exhaust poppet valves is adjusted sothat the intake and exhaust valves open or close when engine cylinderknock windows are open. The output of the knock sensor may be integratednumerically or via an integrator circuit to determine the engine knockvalve noise level of the selected cylinder. The engine knock valve noiselevel (e.g., Cyl_vlv_noise (j)) may be determined via subtracting theengine knock base background noise level of the selected cylinder fromthe integrated knock sensor output value determined after the intake andexhaust valve timing has been adjusted to open or close during an openknock window of the selected cylinder. Method 200 proceeds to 248.

At 248, method 200 judges if engine knock base background noise levelsand the engine knock valve noise levels at the present engine speed havebeen determined for all engine cylinders. Method 200 may keep a recordof which engine knock base background noise levels and engine knockvalve noise levels have been updated for particular engine speeds andloads. If method 200 judges that engine knock base background noiselevels and the engine knock valve noise levels at the present enginespeed have been determined for all engine cylinders, then the answer isyes and method 200 proceeds to 250. Otherwise, the answer is no andmethod 200 proceeds to 249.

At 249, method 200 selects a new engine cylinder for leaning andevaluating the engine knock base background noise level and an engineknock valve noise level. A unique engine knock base background noiselevel and a unique engine knock valve noise level may be determined foreach engine cylinder at selected engine speeds and loads. Further,unique engine knock base background noise levels and unique engine knockvalve noise levels for each engine operating mode, engine speed, andengine load may be determined. However, since the engine is operating inDFSO mode at zero cylinder load, the values of all engine knock basebackground noise levels and engine knock valve noise levels are notdetermined at 246. Method 200 may select a new cylinder to evaluate forengine knock base background noise levels and engine knock valve noiselevels via incrementing, decrementing, or otherwise adjusting the valueof j. Method 200 returns to 246 after selecting a new engine cylinder tolearn and evaluate engine knock base background noise levels and theengine knock valve noise levels.

At 250, method 200 judges if all engine knock base background noiselevels determined at 246 are within a threshold value of an averagevalue of the engine knock base background noise levels determined at246. If so, the answer is yes and method 200 proceeds to 251. Otherwise,the answer is no and method 200 proceeds to 252.

At 252, method 200 requests diagnostics for the knock sensor of theselected cylinder that has a higher or lower engine knock basebackground noise than is expected (e.g., cylinders that exhibit engineknock base background noise levels that are greater or less than theaverage value determined at 250 plus or minus the threshold valuedescribed at 250). The threshold value may be empirically determined viarotating the engine with a dynamometer and recording engine knock basebackground noise levels for the engine cylinders. The diagnostic mayinclude applying a voltage to the knock sensor or causing a cylinder toknock and monitoring knock sensor output to determine whether or not theknock sensor is performing as expected. Method 200 proceeds to 254.

At 251, method 200 stores engine knock base background noise levels andengine knock valve noise levels determined at 246 to controller memory.The engine knock base background noise levels and the engine knock valvenoise levels stored to controller memory may be retrieved from memory todetermine the presence or absence of engine knock when combustion isresumed in the engine and the engine is operating at a speed near thepresent engine speed at which engine knock base background noise levelswere determined. By learning engine knock base background noise levelsand engine knock valve noise levels when the engine is not operating(e.g., combusting fuel), it may be possible to learn fewer engine knockbase background noise levels and fewer engine knock valve noise levelswhen the engine is operating. In particular, the engine knock basebackground noise levels and engine knock noise levels determined whenthe engine was in DFSO mode may be applied when the engine is combustingfuel in all cylinders or in VDE modes so that engine operation while theengine is running may not have to be changed to determine engine knockbase background noise levels and engine knock valve noise levels. Method200 proceeds to 254.

At 254, method 200 judges if vehicle operating conditions are present toexit DFSO mode. In one example, the engine may exit DFSO mode whendriver demand torque exceeds a threshold level. The engine may also exitDFSO mode when the driver demand torque exceeds a threshold even beforeall the instructions of FIG. 4 are completed. If method 200 judges thatconditions are present to exit DFSO mode, then the answer is yes andmethod 200 proceeds to 208. Otherwise, the answer is no and method 200returns to 244.

At 260, selects an actual total number of cylinders that are active tomeet the driver demand torque. The driver demand torque may bedetermined from accelerator pedal position and vehicle speed. Theaccelerator pedal position and vehicle speed may reference a table orfunction of empirically determined value of driver demand torque, whichmay be requested as an engine torque or a wheel torque. The table orfunction outputs the driver demand torque and driver demand torque andvehicle speed may reference second table that outputs an actual totalnumber of cylinders to activate. The actual total number of cylinders toactivate may be a least actual total number of engine cylinders that mayprovide the driver demand torque at the present engine speed. Method 200proceeds to 262 after determining the actual total number of cylindersto activate.

At 262, method 200 selects an engine operating mode and cylinder pattern(e.g., cylinders that combust fuel in the engine operating mode). Theengine operating mode (e.g., stationary VDE four cylinder mode (fouractive cylinders) with a firing order of 1-7-6-4, a rolling VDE modewith firing density of ⅔, etc.) may be selected from the actual totalnumber of cylinders to activate as determined at 260. The engineoperating modes may include activated and deactivated engine cylinders.Alternatively, the engine operating mode may be selected via a statemachine with inputs of driver demand torque and engine speed or vehiclespeed. In one example, the engine operating mode may be selected fromengine operating modes that are available at the present driver demandtorque and engine speed. Engine operating modes that are available maybe a function of engine temperature, engine speed, engine noise andvibration, and other engine and vehicle operating conditions. Method 200selects an engine operating mode according to the actual total number ofcylinders selected to operate at 260 and other engine and vehicleoperating conditions. Method 200 proceeds to 264.

At 264, method 200 operates the engine in the selected VDE operatingmode with the selected actual total number of active cylinders that weredetermined at 260. The controller may activate and/or deactivatecylinders via ceasing to flow fuel to deactivated cylinders and flowingfuel to activated cylinders during cycles of the engine. Further, intakeand exhaust poppet valves of deactivated cylinders may be held closedfor longer than an engine cycle. Intake and exhaust poppet valves ofactivated cylinders are opened and closed during an engine cycle. Method200 may flow fuel to the engine via opening fuel injectors. Method 200may cease flow of fuel to engine cylinders via closing fuel injectors.Method 200 may deactivate intake and exhaust poppet valves via variablevalve actuators. Method 200 proceeds to 266 after the engine enters theselected engine operating mode with the selected cylinder pattern.

At 266, method 200 judges if it is desirable to learn contributions(e.g., Cyl_base_noise (j), Cyl_inj_noise (j), and Cyl_vlv_noise (j)) ofengine knock background noise levels at the present engine speed andengine load. Method 200 may judge that it is desirable to learn engineknock background noise levels at the present engine speed if engineknock indication levels are greater or less than is expected for thepresent engine speed. In addition, method 200 may judge that it isdesirable to learn engine knock background noise levels at the presentengine speed if engine knock background noise levels have not beendetermined for a predetermined amount of time or a predetermineddistanced traveled by the vehicle. If method 200 judges that it isdesirable to learn engine knock background noise levels at the presentengine speed and load, the answer is yes and method 200 proceeds to 268.Learning engine knock background noise levels may be requested when theanswer is yes. If method 200 judges that it is not desirable to learnengine knock background noise levels at the present engine speed andload, then the answer is no and method 200 proceeds to 274.

At 268, method 200 determines contributions (e.g., Cyl_base_noise (j),Cyl_inj_noise (j), and Cyl_vlv_noise (j)) of engine knock backgroundnoise at the present engine speed and load via knock windows associatedwith one or more deactivated engine cylinders or via one or more newlycreated crankshaft angular windows during which output of a knock sensoris sampled via the controller. The engine may operate with one or moredeactivated cylinders (e.g., cylinders that are not combusting fuel)when the engine operates in a VDE mode. Knock cannot be present inengine cylinders that are deactivated since fuel is not combusted indeactivated cylinders.

A knock window that is associated with a particular cylinder is a knockwindow in which knock sensor output is evaluated for the purpose ofdetermining knock in the particular cylinder during a cycle of anengine. However, the knock window may still be associated with theparticular cylinder even if it is not applied for the purpose ofdetermining knock in the particular engine cylinder because each enginecylinder may be allocated an amount of controller computationalresources for detecting engine knock, including generating a knockwindow and sampling a knock sensor during the knock window.Consequently, a knock window that is associated with a particularcylinder may be adjusted to open and close at times when knock is notexpected to occur within the particular cylinder. Yet, the knock windowmay still be considered associated with the cylinder since controllercomputational resources that may be allocated to determine the presenceor absence of engine knock in the particular cylinder are applied togenerate the knock window even though timing of the knock window may notallow for knock detection in the particular cylinder. The duration ofthe knock window of the cylinder that is deactivated may be shortened orreduced (e.g., the knock window may be open for fewer crankshaftdegrees) when the knock window of the cylinder that is deactivated isapplied to determine contributions of engine knock background noise atthe present engine speed and load as compared to when the knock windowof the cylinder that is deactivated is applied to detect knock in anactivated cylinder. By reducing the duration of the knock window, it maybe possible to isolate noise from specific noise sources (e.g., poppetvalves or fuel injectors) from other noise sources so that a level ofnoise from the specific noise source may be more accuratelycharacterized. A more accurate characterization of a noise level from anoise source may improve detection of knock.

Alternatively, instead of describing adjusting timing of a knock windowthat is associated with a particular cylinder, a knock window of aparticular cylinder may be discontinued (e.g., a knock window associatedwith the particular cylinder) and it may be replaced via differentcrankshaft angular interval where output of a knock sensor is sampled ormeasured via the controller. The total number of crankshaft intervalswhere one or more knock sensors are sampled when one or more cylindersis deactivated may be equal to or less than the actual total number ofactivated cylinders plus the actual total number of deactivatedcylinders. An angular interval where output of a knock sensor is sampledneed not be provided for each deactivated cylinder. For example, if twocylinders are deactivated and six cylinders are activated, sevencrankshaft angular intervals where output of one or more knock sensorsis sampled may be provided. The duration of the angular crankshaftinterval where a knock sensor is sampled that replaces the knock windowof an activated cylinder may be shortened or reduced when the crankshaftangular interval where a knock sensor is sampled of the cylinder that isdeactivated is applied to determine contributions of engine knockbackground noise at the present engine speed and load as compared towhen the knock window of the cylinder that is deactivated is applied todetect knock in an activated cylinder. By reducing the duration of thecrankshaft angular interval where a knock sensor output is sampled, itmay be possible to isolate noise from specific noise sources from othernoise sources so that a level of noise from the specific noise sourcemay be more accurately characterized. A more accurate characterizationof a noise level from a noise source may improve detection of knock.

Adjusting the timing and/or duration of the knock window of adeactivated cylinder may also be beneficial to learn the propagationtime of injector or valve noise from the source (injector or valve) tothe knock sensor. The knowledge of the propagation time is important todecide whether the injector or valve noise falls into the knock window.For example, it may be desirable to lean propagation time. A knockwindow of cylinder i may starts at 5 degrees after TDC (firing) ofcylinder i, and it may end at 40 degrees after TDC. Fuel injectorclosing of cylinder j may occur at 1 degree after TDC (firing) ofcylinder i. The fuel injector closing may occur outside (before) theknock window; however, some time is needed for the noise to propagatefrom the injector to the knock sensor. If the propagation time is 1 ms,then at 1500 RPM, the noise needs 9 CA degrees to reach the knocksensor, and in this example the injector noise will fall in the knockwindow.

In one example, the propagation time may be learned as follows: bystarting the knock window of the deactivated cylinder at differenttimings relative to the noise source (e.g., fuel injector closing, valveclosing, etc.) on different occasions, and observing at which point achange in the background noise level starts, the propagation time may bedetermined. Alternatively, terminating the knock window at differenttimings can be used instead if the noise falls closer to the end of theknock window. Or, the injection or valve timing could be varied instead.Also, adjusting the timing and/or duration of the knock window may beused to learn the (ringing) duration of a fuel injector or poppet valvenoise, and how the noise level varies with a partial breach (e.g., noiseentry into the knock window) of the knock window. For example, the knockwindow of cylinder i may start at 12 degrees after TDC (firing) ofcylinder i, and it may end at 47 degrees after TDC. Fuel injectorclosing of cylinder j may occur at 1 degree after TDC (firing) ofcylinder i. Propagation time for injector noise is 9 crank angle (CA)degrees (at 1500 RPM for example). The fuel injector noise may reach theknock sensor 2 CA degrees before the knock window start. If the durationof the fuel injector noise at 1500 RPM corresponds to 5 CA degrees, then60% of the injector noise signature may fall into the knock window. Inthis case, knock background noise may be some value between the basenoise and base+injector noise that completely falls into the knockwindow (e.g. base noise and base+0.6*injector noise or it can be anon-linear function).

By starting the knock window of the deactivated cylinder at differenttimings relative to the noise source (e.g., injector closing, valveclosing, etc.) on different occasions, it may be determined how thebackground noise level varies with different amounts of partial breaches(e.g., noise entry into the knock window), and determine the noiseduration. Alternatively, terminating the knock window at differenttimings can be used instead if the noise falls closer to the end of theknock window. Or, the injection or valve timing could be varied instead.

Method 200 adjusts timing of a knock window associated with adeactivated cylinder, or alternatively, method 200 ceases providing aknock window associated with the deactivated cylinder and generates anew crankshaft angular window where output of a knock sensor is sampledto determine a contribution of engine background noise. For example, asshown in FIGS. 7 and 9, timing of an engine knock window 702 associatedcylinder number three, may be adjusted or replaced via a new crankshaftangular window where output of a knock sensor is sampled such that theadjusted or new window spans (e.g., begins before and ends after) anevent that generates or influences a contribution of engine backgroundnoise. In particular, knock window 702 in FIG. 7 is moved to the timingshown by window 702 a in FIG. 9. Alternatively, window 702 may bedescribed as being removed or ceased and new knock window 702 a may beprovided in its place since knock window 702 is not needed to detectknock in cylinder three when cylinder three is deactivated.

For example, the knock window associated with cylinder number three, ora new crankshaft angular interval where output of a knock sensor issampled, may be adjusted to any crankshaft angle timing that is desiredto detect a contribution of engine background noise. Thus, openingtiming (e.g., crankshaft angle) of the knock window may be advanced orretarded from an opening timing of the knock window when the knockwindow is applied to detect knock. Further, closing timing (e.g.,crankshaft angle) of the knock window may be advanced or retarded from aclosing timing of the knock window when the knock window is applied todetect knock. The output of the knock sensor sampled during thecrankshaft interval may be integrated to generate a value for thecontribution engine knock background noise. Further, method 200 maysample an output of a first knock sensor when the knock window of aparticular cylinder is provided to determine the presence or absence ofknock in the particular cylinder. However, an output of the first knocksensor, or alternatively, a second knock sensor, may be sampled duringthe adjusted knock window that is associated with the particularcylinder, or alternatively, during the crankshaft angular interval wherea knock sensor is sampled that replaces the knock window that isassociated with the particular cylinder when the particular cylinder isdeactivated and knock is not expected in the particular cylinder. Thecontributions of engine background noise may be determined from thesampled knock sensor output. This allows the controller to observecontributions of engine knock background noise levels with differentknock sensors for knock sensor and engine component diagnostics.

Method 200 may determine contributions (e.g., Cyl_base_noise (j),Cyl_inj_noise (j), and Cyl_vlv_noise (j)) of engine knock backgroundnoise at the present engine speed and load for all available VDE modesand cylinder patterns via applying controller resources for generatingengine knock windows and detecting engine knock in one or moredeactivated engine cylinders. In one example, a table or function mayinclude references to all engine operating modes that are available atthe present engine speed and load as well as all of the contributions ofengine knock background noise that may be determined when the engineoperates in the engine operating modes that are available. Valuesassociated with table entries may be the basis for determining whetheror not a particular contribution of engine background noise for thepresent engine speed and load has been learned or modified recently. Anon-limiting example of adjusting angular crankshaft intervals forsampling knock sensor output via controller computational resources thatwere previously allocated to a presently deactivated cylinder is shownin FIG. 9. Method 200 proceeds to 270 after determining noisecontributions of engine background noise for the present engine speedand load.

At 270, method 200 assesses whether or not knock should be indicated forthe selected cylinder that is being evaluated for engine knock (e.g.,cylinder j). FIG. 9 shows operation of the engine and controllerincluding knock windows and knock sensor sampling (e.g., measuring)according to the method of FIG. 2 for detecting knock when an engine isoperating in a VDE mode and determining engine knock background noiselevels. In one example, method 200 computes a knock intensity value forcylinder j by integrating sampled output of the knock sensor during theopen knock window of cylinder j and divides the integrated knock sensoroutput by the total engine knock background noise level of cylinder jfor the present engine speed and engine load (e.g., Cyl_combined_noise(j)).

The total or combined engine knock background noise level may beexpressed as: Cyl_combined_noise (j)=Cyl_base_noise (j)+Cyl_inj_noise(j)+Cyl_vlv_noise (j), where Cyl_combined_noise (j) is the total engineknock background noise for cylinder j, Cyl_base_noise (j) is the engineknock base background noise for cylinder j, Cyl_inj_noise (j) is thefuel injector noise that is present in the knock window of cylinder j,and Cyl_vlv_noise (j) is the poppet valve noise present in the knockwindow of cylinder (j). Accordingly, any one of the variables in thecombined background noise equation may be solved knowing three of theother variables. For example, Cyl_base_noise (j)=Cyl_combined_noise(j)−Cyl_inj_noise (j)−Cyl_vlv_noise (j).

The total engine knock background noise level may be retrieved fromcontroller memory or it may be determined from individual noisecontributions that have been retrieved from memory as previouslyindicated. If knock is detected, the spark is retarded for cylinder jand then the spark timing is advanced back toward the MBT (minimum sparkadvance for best engine torque at the present engine speed and load)spark timing for cylinder j. If knock is not indicated, spark timing forthe cylinder remains at its requested or base timing (e.g., knocklimited spark timing or MBT timing). The presence or absence of engineknock for each cylinder may be determined in this way. The cylindernumber j may be adjusted according to an engine firing order each enginecycle (e.g., two revolutions) so that knock is evaluated for each enginecylinder each engine cycle. Method 200 proceeds to 272 after adjustingengine spark timing in cylinder j for engine knock.

At 272, method 200 judges if the desired contribution engine knockbackground noise levels at the present engine speed have been determinedfor all engine cylinders. Method 200 may keep a record of whichcontribution engine knock background noise levels have been updated forthe present particular engine speed and load. If method 200 judges thatcomponent engine knock background noise levels at the present enginespeed have been determined for all engine cylinders, then the answer isyes and method 200 proceeds to 274. Otherwise, the answer is no andmethod 200 proceeds to 273.

At 273, method 200 selects a new knock window to use to detectcontribution engine knock background noise. For example, if cylindernumber two is deactivated, then method 200 may adjust timing of theknock window associated with cylinder number two to determinecontribution engine knock background noise levels. Alternatively, theknock window associated with cylinder number two may be discontinued anda new crankshaft angular interval where output of a knock sensor issampled may be generated to determine contribution engine knockbackground noise levels. Method 200 returns to 262.

At 274, method 200 judges if vehicle operating conditions are present toexit VDE mode. In one example, the engine may exit VDE mode when driverdemand torque exceeds a first threshold level or is reduced below asecond threshold level. If method 200 judges that conditions are presentto exit VDE mode, then the answer is yes and method 200 proceeds to 210.Otherwise, the answer is no and method 200 returns to 262.

At 280, method 200 selects the cylinder for which the cylinder'sbackground noise levels are to be learned and updated. In one example,the selected cylinder is the cylinder for which it is desired to adjustan engine knock background noise level. For example, if it is desired toupdate or learn the engine knock background noise level for cylindernumber one, then cylinder number one may be the selected cylinder. Logicfor selecting the engine cylinder may be stored in controller memory. Inone example, cylinder number one is first selected and then the selectedcylinder (j) is incremented by a value of one until each cylinder hasbeen selected and the engine knock background noise levels of eachengine cylinder have been established.

At 282, method 200 judges if it is desirable to learn contributions(e.g., Cyl_base_noise (j), Cyl_inj_noise (j), and Cyl_vlv_noise (j)) ofengine knock background noise levels at the present engine speed andengine load. If method 200 judges that it is desirable to learn engineknock background noise levels at the present engine speed and load, theanswer is yes and method 200 proceeds to 284. Learning engine knockbackground noise levels may be requested when the answer is yes. Ifmethod 200 judges that it is not desirable to learn engine knockbackground noise levels at the present engine speed and load, then theanswer is no and method 200 proceeds to 288.

At 284, method 200 adjusts engine load to meet driver demand torque whenspark of the selected cylinder is retarded to reduce the possibility ofengine knock. In one example, engine load may be increased by increasingair flow through the engine via opening the engine's throttle. Enginetorque may be maintained to meet driver demand torque by increasing theengine load even though spark timing of the selected cylinder may beretarded.

Method 200 also operates N−1 cylinders with knock limited spark timing(e.g., spark timing where engine knock begins to be observed) or MBTspark timing while the spark timing of the selected cylinder is retardedfrom knock limited spark timing or MBT spark timing, where N is thetotal actual number of engine cylinders. By retarding the spark timingof the selected cylinder, the possibility of knock in the selectedcylinder may be significantly reduced so that an accurate estimate ofbackground engine noise for the selected cylinder may be determined.

Method 200 determines a combined background noise levelCyl_combined_noise (j) for the selected cylinder. In one example, method200 integrates output of a knock sensor during a portion of the openknock window of the selected cylinder. The output of the knock sensormay be integrated numerically or via an integrator circuit to determinethe base background noise level of the selected cylinder. Method 200stores the value of the combined background noise level to controllermemory. The combined background noise level may include noise frominjectors opening and/or closing during the open knock window and/orpoppet valves opening and/or closing during the open knock window. Thecombined background noise level for a cylinder may be useful fordetermining the contributions of noise sources. The combined backgroundnoise may be expressed as Cyl_combined_noise (j)=Cyl_base_noise(j)+Cyl_inj_noise (j)+Cyl_vlv_noise (j). Accordingly, any one of thevariables in the combined background noise equation may be solvedknowing three of the other variables. For example, Cyl_base_noise(j)=Cyl_combined_noise (j)−Cyl_inj_noise (j)−Cyl_vlv_noise (j).

Next, method 200 adjusts intake and exhaust valve timing of one or morecylinders so that intake and/or exhaust valves do not close during theopen engine knock window of the selected cylinder. Alternatively, oradditionally, method 200 adjusts intake and exhaust valve timing of oneor more cylinders so that intake and/or exhaust valves do not openduring the open engine knock window of the selected cylinder. Byremoving the intake and exhaust valve opening and closing noise from anopen knock window of the selected cylinder, it may be possible determinea more accurate value of base engine background noise level. Inaddition, adjustments to throttle position may be made to maintainengine torque when poppet valve timings are adjusted.

Method 200 also adjusts direct injection fuel injector timing of one ormore cylinders so that DI fuel injectors are not opened or closed duringthe open engine knock window of the selected cylinder. Adjusting thetiming of the DI injector includes deactivating a DI injector andactivating a port fuel injector so that noise from the DI injector doesnot enter the open knock window of the selected cylinder. Thus, DIinjectors that open or close during the open knock window of theselected cylinder may be adjusted from a base timing of a DI injector soas to remove noise from DI injectors that open or close during the openknock window of the selected cylinder. By removing the DI injector noisefrom an open knock window of the selected cylinder, it may be possibledetermine a more accurate value of base engine background noise level.

Method 200 determines a base background noise level Cyl_base_noise (j)for the selected cylinder via integrating output of a knock or vibrationsensor during a portion of the open knock window of the selectedcylinder. The output of the knock sensor may be integrated numericallyor via an integrator circuit to determine the base background noiselevel of the selected cylinder. Method 200 stores the value of the basebackground noise level to controller memory.

Method 200 adjusts direct injection fuel injector timing of one or morecylinders so that DI fuel injectors of all cylinders operate at theirbase timings or timings that provide similar noise levels in the knockwindow. Thus, one or more DI injectors may open or close during the openengine knock window of the selected cylinder. Adjusting the timing ofthe DI injector includes reactivating one or more DI injectors anddeactivating one or more port fuel injectors so that noise from the DIinjector that may enter the open knock window of the selected cylindermay be determined. By adding the DI injector noise to the open knockwindow of the selected cylinder, it may be possible determine the noisecontribution of one or more DI injectors to the total engine backgroundnoise level. Further, timings of fuel injections may be adjusted tocapture both opening and closing of a fuel injector during a knockwindow. Further still, it may be desirable to change fuel injectorclosing time or opening time or crankshaft position so that a larger orsmaller amount of noise generated from opening or closing the fuelinjector may be determined. Operation of the fuel injector may induce avibration and sound from the engine block that has a duration that islonger than just the exact time the fuel injector closes. Consequently,timing or crankshaft angle where the fuel injector opens or closes maybe moved so that it is closer to the center of the knock window. In thisway, the total amount of noise generated by the fuel injector may bedetermined. This may be beneficial for applications where fuel injectiontiming is advanced or retarded since advancing or retarding the fuelinjection may change the engine background noise level, which may affectdetection of knock. Consequently, by advancing or retarding fuelinjector opening and/or closing times or crankshaft angles, engine knockbackground noise levels may be more accurately characterized and knockcontrol may be improved.

Method 200 determines a DI injector background noise level Cyl_inj_noise(j) for the selected cylinder. In one example, method 200 integratesoutput of a knock sensor during a portion of the open knock window ofthe selected cylinder and then the base background noise levelpreviously determined is subtracted from the integrated value. Theresult is the contribution of DI injector noise to the total cylinderbackground noise level for the selected cylinder. The output of theknock sensor may be integrated numerically or via an integrator circuitto determine the contribution of DI injector noise to the total cylinderbackground noise level for the selected cylinder. Method 200 stores thevalue of the contribution of DI injector noise to the total cylinderbackground noise level for the selected cylinder to controller memory.

Then, method 200 adjusts direct injection fuel injector timing of one ormore cylinders so that DI fuel injectors are not opened or closed duringthe open engine knock window of the selected cylinder. Thus, DIinjectors that open or close during the open knock window of theselected cylinder may be adjusted from a base timing of a DI injector soas to remove noise from DI injectors that open or close during the openknock window of the selected cylinder. By removing the DI injector noisefrom an open knock window of the selected cylinder, it may be possibleto determine a more accurate value of noise from intake/exhaust valvesthat open and/or close during a knock window of the selected cylinder.

Method 200 adjusts intake and/or exhaust valve timing of one or morecylinders so that poppet valve opening and closings of all cylindersoperate at their base timings. Thus, one or more poppet valves may openor close during the open engine knock window of the selected cylinder.By adding the poppet valve noise to the open knock window of theselected cylinder, it may be possible to determine the noisecontribution of one or more intake and/or exhaust poppet valves to thetotal cylinder background noise level for the selected cylinder. Inaddition, it may be desirable to change intake and/or exhaust poppetvalve closing time, opening time, opening crankshaft position, orclosing crankshaft position so that a larger or smaller amount of noisegenerated from opening or closing the poppet valve may be determined.Operation of a poppet valve may induce a vibration and sound from theengine block that has a duration that is longer than just the exact timethe poppet opens or closes. Consequently, timing or crankshaft anglewhere the poppet valve opens or closes may be moved so that it is closerto the center of the knock window. In this way, the total amount ofnoise generated by the poppet valve may be determined. This may bebeneficial for applications where poppet valve timing is advanced orretarded since advancing or retarding the poppet valves may change theengine background noise level, which may affect detection of knock.Consequently, by advancing or retarding poppet opening and/or closingtimes or crankshaft angles, engine knock background noise levels may bemore accurately characterized and knock control may be improved.

Method 200 determines a poppet valve background noise levelCyl_vlv_noise (j) for the selected cylinder. In one example, method 200integrates output of a knock sensor during a portion of the open knockwindow of the selected cylinder and then the base background noise levelpreviously determined is subtracted from the integrated value. Theresult is the contribution of poppet valve noise to the total cylinderbackground noise level for the selected cylinder. The output of theknock sensor may be integrated numerically or via an integrator circuitto determine the contribution of poppet valve noise to the totalcylinder background noise level for the selected cylinder. Method 200stores the value of the contribution of poppet valve noise to the totalcylinder background noise level for the selected cylinder to controllermemory. Method 200 proceeds to 286.

At 286, method 200 judges if all desired engine knock background noiselevels at the present engine speed have been determined. Method 200 maykeep a record of which engine knock base background noise levels andengine knock valve noise levels have been updated for particular enginespeeds and loads. If method 200 judges that engine knock backgroundnoise levels have been determined for all engine cylinders, then theanswer is yes and method 200 proceeds to 288. Otherwise, the answer isno and method 200 proceeds to 287.

At 287, method 200 selects a new engine cylinder for leaning andevaluating the engine knock background noise levels. Method 200 returnsto 282 after selecting a new engine cylinder to learn and evaluateengine knock background noise levels.

At 288, method 200 judges if vehicle operating conditions are present toexit no knock conditions. In one example, the engine may exit no knockconditions when driver demand torque exceeds a first threshold leveland/or when engine temperature is greater than a threshold temperature.If method 200 judges that conditions are present to exit no knock mode,then the answer is yes and method 200 proceeds to 212. Otherwise, theanswer is no and method 200 returns to 282.

Thus, the method of FIGS. 2-6 provides for an engine operating method,comprising: ceasing to supply fuel to a first engine cylinder via acontroller; reducing a crankshaft duration of a knock window of thefirst engine cylinder from a first duration when the knock window isapplied to evaluate the presence of knock in a cylinder to a secondduration when the knock window is applied to quantify an engine knockbackground noise level; and sampling output of a knock sensor during theknock window via the controller. The method further comprises generatingthe engine knock background noise level via sampling output of the knocksensor. The method further comprises generating an indication of engineknock via the engine knock background noise level. The method furthercomprises adjusting a crankshaft angle where the knock window opens. Themethod further comprises adjusting a crankshaft angle where the knockwindow closes. The method further comprises spanning an event of a noisegenerating device via the knock window. The method includes where theevent is a closing of the noise generating device, and where the deviceis a fuel injector or a poppet valve. The method includes where theevent is an opening of the noise generating device, and where the deviceis a fuel injector or a poppet valve.

The method of FIGS. 2-6 also provides for an engine operating method,comprising: adjusting timing of an engine actuator via a controller toincrease or decrease engine noise generated during a knock windowassociated with cylinder in response to a request to learn an engineknock background noise level; and sampling output of a knock sensorduring the knock window via controller. The method further comprisesceasing to supply fuel to one or more cylinders before and while timingof the device is adjusted. The method includes where the knock window isa knock window associated with a deactivated cylinder. The methodincludes where adjusting timing of the engine actuator includesadvancing timing of the engine actuator relative to a crankshaftposition. The method includes where adjusting timing of the engineactuator includes retarding timing of the engine actuator relative to acrankshaft position. The method includes where the engine actuator is afuel injector or a poppet valve. The method further comprises sampling afirst knock sensor during the knock window associated with the cylinderbefore the request to learn the engine knock background noise level andsampling a second knock sensor during the knock window associated withthe cylinder in response to the request to learn the engine knockbackground noise level.

Referring now to FIG. 7, a timing sequence 700 that illustrates examplebase engine knock window timing, direct injector timing, and intake andexhaust poppet valve opening and closing timing is shown. The sequenceapplies to when the presence or absence of knock in engine cylinders isbeing evaluated and/or detected. The illustrated timings are for aneight cylinder engine that has a firing order of 1-3-7-2-6-5-4-8. Theengine is a four stroke engine that has a cycle of 720 crankshaftdegrees. The engine crankshaft degrees are located along the horizontalaxis and zero degrees represents top-dead-center compression stroke forcylinder number one. The eight cylinders are labeled along the verticalaxis. In this example, several engine knock background noise influencesare shown visually by DI injections and poppet valve timings.

The engine knock windows for each cylinder are positioned at a level ofa tick mark along the vertical axis that is associated with the knockwindow. For example, the engine knock window for or associated withcylinder number one is indicated by slash bar 701. Knock windows for theremaining engine cylinders (2-8) are indicated by bars (702-708) thatalign with labeling along the vertical axis. The controller may sample(e.g., measure) output of the knock sensor when a knock window of acylinder is open. An open knock window is a crankshaft region whereengine knock may be expected for a particular engine cylinder. The knockwindow bars indicate when the respective knock windows are open.

Knock window 701 includes a slash pattern that indicates that output ofknock sensor 90 a is sampled during the open knock window of cylindernumber one. Knock window 704 includes the same slash pattern thatindicates that output of knock sensor 90 a is sampled during the openknock window of cylinder number two. Knock window 702 includes a plaidpattern that indicates that output of knock sensor 90 b is sampledduring the open knock window of cylinder number three. Knock window 707also includes a plaid pattern that indicates that output of knock sensor90 b is sampled during the open knock window of cylinder number four.Knock window 706 includes a horizontal line pattern that indicates thatoutput of knock sensor 90 c is sampled during the open knock window ofcylinder number five. Knock window 705 includes the same horizontal linepattern that indicates that output of knock sensor 90 c is sampledduring the open knock window of cylinder number six. Knock window 703includes a vertical line pattern that indicates that output of knocksensor 90 d is sampled during the open knock window of cylinder numberseven. Knock window 708 also includes a vertical line pattern thatindicates that output of knock sensor 90 d is sampled during the openknock window of cylinder number eight. Thus, the knock sensor that issampled during a particular knock window is indicated by the patterncontained within the knock window.

The engine fuel injection timings for each cylinder are positioned at alevel the tick mark along the vertical axis that is associated with thefuel injection. For example, solid bar 710 represents a DI fuel injectoropen interval for cylinder number two. The DI fuel injector for cylindernumber two is closed when solid bar 710 is not visible. The DI fuelinjector for cylinder number two opens at the left side of solid bar 710and closes at the right side of solid bar 710. DI fuel injections forthe remaining engine cylinders (2-8) are indicated by similar solid bars(711-717) and they follow the same convention as solid bar 710. The fuelinjector bars 710-717 respectively align with cylinders listed along thevertical axis that the fuel injector bars correspond to.

The strokes of a cylinder are positioned just above a level the tickmark along the vertical axis that is associated with the stroke. Forexample, strokes for cylinder number one are indicated by horizontallines 720-723. Letters p, e, i, and c identify the power (p), exhaust(e), intake (j), and compression (c) strokes associated with cylindernumber one. Strokes for the other engine cylinders are identified in asimilar way by lines 725-758.

The exhaust valve timings for each cylinder are positioned above a levelthe tick mark along the vertical axis that is associated with theexhaust valve timings. For example, exhaust valve opening time forcylinder number one is indicated by cross-hatched bar 760. The exhaustvalves for cylinder number one are closed when no cross-hatched bar ispresent above the cylinder strokes of cylinder number one. Exhaust valveopening times for the other cylinders are indicated at 762, 764, 767,770, 772, 774, 775, 777, and 778.

The intake valve timings for each cylinder are positioned above a levelthe tick mark along the vertical axis that is associated with the intakevalve timings. For example, intake valve opening time for cylindernumber one is indicated by dotted bar 761. The intake valves forcylinder number one are closed when no dotted bar is present above thecylinder strokes of cylinder number one. The intake valve opening timesfor the other cylinders are indicated at 763, 765, 766, 768, 769, 771,773, 776, and 779.

The noise observed in a knock window of one cylinder may include noiserelated to events associated with other engine cylinders. For example,the engine knock window of cylinder number two indicated at 704 mayoccur at a time when the knock sensor is exposed to noise from the DIinjection to cylinder number four at 713 if the fuel injection intocylinder number four begins or ends (e.g., the fuel injector opens orcloses) when knock window 704 is open. In this example, DI injection 713opens when knock window 704 is open and closes after knock window 704closes. Arrow 793 indicates this relationship. Thus, the DI at 713 maybe partially captured in knock window 704. Similar relationships betweenDI injections to other cylinders and knock windows are show for theother engine cylinders and indicated via arrows 790-797.

Thus, in this example, the engine knock background noise leveldetermined for the engine knock window of cylinder number two shown at704 may include noise generated by opening the DI injector at 713. Inaddition, the intake valve closing of cylinder number five indicated bydotted bar 773 shows that the intake valve of cylinder number fivecloses and may generate noise within the time that the knock window ofcylinder number two is open as shown by bar 704. Further, the exhaustvalve closing of cylinder number eight indicated by dotted bar 778 showsthat the exhaust valve of cylinder number eight closes and may generatenoise within the time that the knock window of cylinder number two isopen as shown by bar 704. Further still, the exhaust valve opening ofcylinder number seven indicated by bar 764 shows that the exhaust valveof cylinder number seven opens and may generate noise within the timethat the knock window of cylinder number two is open as shown by bar704. Consequently, in this example, engine background noise asdetermined via the engine knock window for cylinder number two at 704may include noise from DI event 713 and noise from valve closing eventof valve timing 773, valve opening event at valve timing 764, and valveclosing event at valve timing 778.

The poppet valve and DI injection times shown in FIG. 7 may beindicative of base DI and poppet valve timings. These timings may affectthe engine background noise levels determined from engine knock windowsof the cylinders (e.g., 704). While it may be desirable to include allbackground noise sources to determine a background noise level for aparticular cylinder, it may also be useful to decompose a totalbackground noise level into the contributions from individual noisesources. By removing one or more noise influences from a total enginebackground noise level, it may be possible to determine engine noiselevels that may be used to determine whether or not knock is present inother cylinders. For example, an engine knock base background noiselevel for cylinder number one may be used as an engine knock basebackground noise level for cylinder number three. Further, the poppetvalve noise or DI injector noise of one cylinder may be applied to adifferent cylinder to estimate engine knock background noise for thedifferent cylinder. Such allocations of engine knock background noiselevels may be useful when an engine knock background noise level has notbeen observed for a particular engine cylinder or if opportunities forlearning engine knock background noise levels is limited by vehicleoperating conditions. The sequence of FIG. 7 may be provided via themethod of FIGS. 2-6.

Referring now to FIG. 8, a timing sequence 800 that illustrates examplebase engine knock window timing for an engine operating in VDE fourcylinder mode is shown. The illustrated timings are for an eightcylinder engine that has a firing order of 1-3-7-2-6-5-4-8. The engineis a four stroke engine that has a cycle of 720 crankshaft degrees. Theengine crankshaft degrees are located along the horizontal axis and zerodegrees represents top-dead-center compression stroke for cylindernumber one. The eight cylinders are labeled along the vertical axis. Inthis example, several engine knock background noise influences have beenremoved from the engine knock window of cylinder number two to show howa base engine knock background noise level of cylinder number two may bedetermined and learned. However, noise from DI 713 a is fully capturedin knock window 704. Knock is controlled and engine knock backgroundnoise levels are determined in the sequence of FIG. 8. The sequence ofFIG. 8 may be provided via the method of FIGS. 2-6. A bar above acylinder number along the vertical axis indicates that the cylinder isdeactivated (e.g., not combusting fuel).

Since the engine is in VDE mode, fuel is not injected into deactivatedcylinders and poppet valves of deactivated cylinders are held closed forthe entire engine cycle, but poppet valves and direct injectors continueto operate in active cylinders. In this example, the poppet valvetimings of the activated cylinders are adjusted (e.g., advanced orretarded relative to base timings shown in FIG. 7) so that engine knockbase background noise levels for the cylinders may be determined. Thus,poppet valves do not open and close during knock window 704. However, DI713 a is fully captured in knock window 704 because DI 713 a beginsafter knock window 704 opens and DI 713 a closes before knock window 704closes. Engine strokes and knock windows for each of the cylinders shownin FIG. 8 are identical to those shown in FIG. 7, except as noted below.Therefore, for the sake of brevity, the description of these items willnot be repeated. Nevertheless, the timings and sequence shown in FIG. 8is identical to that shown in FIG. 7, except as noted.

In this example, poppet valve closings and DI injector closings havebeen removed from the knock window of each cylinder so that an engineknock injector background noise level of some cylinders may beestablished by integrating the output of an engine knock sensor duringthe engine knock window of the cylinder. For example, the engine knockwindow for cylinder number two during this engine cycle is indicated bybar 704 and timing of the exhaust valve indicated at 764 a has beenmodified so that the exhaust valve does not open when knock window 704is open. Likewise, valve timings 760 a, 7161, 765 a, 769 a, 770 a, 775a,776 a, and 777 a have been adjusted to remove poppet valve opening andclosing noise from timings (e.g., crankshaft angles) when knock windows701-708 are open so that engine knock injection background noise levelsmay be established for some cylinders and engine knock base backgroundnoise may be established for each cylinder.

As an example, the engine knock injector background noise level ofcylinder number two may be determined via integrating output of avibration based knock sensor during at portion of open knock window 704.This engine knock injector background noise level may be applied todetermine the presence of knock in cylinder number two or other enginecylinders. Further, an engine knock base background noise level forcylinder number seven may be determined and this engine knock basebackground noise level does not include noise from DI injectors orpoppet valves opening and closing while knock window 703 is open so thatinfluence of injector and valve opening and closing may be reduced. Thepoppet valve timings shown in FIG. 8 may be indicative of modifiedpoppet valve timings for determining engine knock injection backgroundnoise levels and engine knock base background noise levels.

It should also be noted that the opening and closing times or crankshaftangles of the poppet valve timings shown in FIG. 8 may be adjusted tofall within knock windows 701-708 so that contributions of poppet valvesopening and closing to a total or combined engine knock background noiselevel may be determined. In one example, a value of an engine knock basebackground noise level of a cylinder may be subtracted from a value ofengine knock background noise that includes valve openings and closingsduring the knock window to generate the engine knock valve noise level.

Referring now to FIG. 9, a timing sequence 900 that illustratesadjusting timing of a knock window that is associated with a deactivatedcylinder to determine engine knock background noise levels is shown. Theillustrated timings are for an eight cylinder engine that has a firingorder of 1-3-7-2-6-5-4-8. The engine is a four stroke engine that has acycle of 720 crankshaft degrees. The engine crankshaft degrees arelocated along the horizontal axis and zero degrees representstop-dead-center compression stroke for cylinder number one. The eightcylinders are labeled along the vertical axis. In this example, portinjections have been provided so that direct fuel injectors do not closeduring knock windows of engine cylinders. Further, instead of samplingoutput of a first knock sensor that is applied to detect knock in afirst cylinder during a knock window associated with a first cylinderwhen knock may be expected in the first cylinder, output of a secondknock sensor is sampled during the knock window associated with thefirst cylinder so that engine noise sources may be sampled fromdifferent locations to improve diagnostics and improve signal to noisecharacteristics for detecting noise from various engine noise sources(e.g., fuel injectors, poppet valves, front end accessories, etc.).

The fuel injections, valve timings, cylinder strokes, and engineposition for each of the cylinders shown in FIG. 9 are identical tothose shown in FIG. 7, except as noted below. Therefore, for the sake ofbrevity, the description of these items will not be repeated.Nevertheless, the timings and sequence shown in FIG. 9 is identical tothat shown in FIG. 7, except as noted.

In this example, the engine is operating in a stationary VDE mode wherecylinders 3, 2, 5, and 8 are deactivated as indicated by the bars abovethe respective cylinder labels. This allows knock windows of one or moredeactivated cylinders to capture and determine levels of noise fromspecific noise sources. The timing of knock windows associated withdeactivated engine cylinders may be adjusted so that the knock windowsassociated with deactivated engine cylinders are open and span (e.g.,knock windows open before and close after the noise event to be measuredor observed) noise generating events (e.g., intake and exhaust poppetvalve openings and closings, fuel injector openings and closings, etc.).

Alternatively, this may be described as ceasing to generate a knockwindow for a deactivated cylinder and generating a new crankshaft windowwhere a knock sensor is sampled to determine a noise level generated byan event (e.g., opening or closing of a device) of a noise source. Thus,if an engine has eight cylinders and eight knock windows are generatedto observe knock in the eight cylinders during conditions when theengine may be expected to knock, then eight crankshaft angular intervalswhere one or more knock sensors are sampled may be generated when one ormore cylinders are deactivated. However, timings of a total number ofangular intervals where knock sensors are sampled may be adjusted forthe total number of deactivated cylinders. For example, if the engine isan eight cylinder engine and two cylinders are deactivated during anengine cycle, then eight angular intervals where knock sensor output issampled may be provided, but timing of two of the eight angularintervals may be adjusted to different timings so that noise generatedby noise sources may be isolated and characterized. Timing of the sixother angular intervals where knock sensor output is sampled may remainunchanged so that the presence or absence of knock in activatedcylinders may be determined. In this way, computational resources of thecontroller may be reallocated to characterize noise levels generated byengine noise sources. The characterized noise levels may then be thebasis for determining the presence or absence of knock in enginecylinders.

Timing of knock windows 702 a and 704 a associated with deactivatedcylinders 3 and 2 is adjusted as compared to base knock window timingsthat are shown in FIG. 7. In particular, the angular duration of knockwindow 702 a is shorter than that of knock window 702 shown in FIG. 7.Further, knock window opening and closing times or crankshaft angles ofknock window 702 a are changed to a later time or crankshaft angle. Inaddition, the angular duration of knock window 704 a is shorter thanthat of knock window 704 shown in FIG. 7. Also, knock window opening andclosing times or crankshaft angles of knock window 704 a are changed toa later time or crankshaft angle.

This knock window timing changes allow noise from closing of the portfuel injector shown at injection timing bar 717 a to be determined viasampling a knock sensor during knock window 702 a without beinginfluenced by noise from the intake valve opening indicated by bar 768.Further, noise from closing the intake valve indicated by bar 761 may bedetermined via knock window 704 a without being influenced by noise fromthe exhaust valve closing indicated by bar 764. Thus, it may be observedthat the opening timing of knock window 704 a is shortened and movedfrom an expansion stroke of cylinder number two into an exhaust strokeof cylinder number two or an intake stroke of cylinder number one.Further, it may be observed that the opening timing of knock window 702a is shortened and moved from an expansion stroke of cylinder numberthree into an intake stroke of cylinder number three or an intake strokeof cylinder number one. Thus, a knock window of a cylinder may be movedfrom an expansion or power stroke of a cylinder to a different stroke ofthe cylinder (e.g., intake, exhaust, compression) to detect andcharacterize a level of noise of an engine noise source. Output of aknock sensor is sampled and integrated in the new or shifted knockwindow to determine a noise level (e.g., Cyl_base_noise (j),Cyl_combined_noise (j), Cyl_inj_noise (j), Cyl_vlv_noise (j)) of thecylinder (j). The noise level may be applied not just to cylinder (j) todetermine combined or total noise of the cylinder, but to other enginecylinders as well to determine combined noise levels for the othercylinders. For example, if cylinder j is cylinder number 3 and the valueof Cyl_inj_noise (j) s 0.5, the injector noise for cylinder number two(Cyl_inj_noise (2)) may be adjusted to 0.5 based on the value ofCyl_inj_noise (j), where (j) is 3.

Additionally, in this example, the knock sensor sampled in knock window702 a is knock sensor 90 d. However, when evaluating cylinder numberthree for knock, knock sensor 90 b is sampled during knock window 702 asshown in FIG. 7. Similarly, the knock sensor sampled in knock window 704a is knock sensor 90 c. However, when evaluating cylinder number two forknock, knock sensor 90 a is sampled during knock window 704 as shown inFIG. 7. By changing which knock sensor is sampled in the knock windowassociated with the deactivated cylinder or that replaces the knockwindow of the deactivated cylinder, it may be possible to improve asignal to noise ratio for detecting a noise level of a particular enginenoise source (e.g., fuel injectors, poppet valves, etc.). Consequently,the estimates of noise levels (e.g., Cyl_base_noise (j),Cyl_combined_noise (j), Cyl_inj_noise (j), Cyl_vlv_noise (j)) may beimproved.

FIG. 9 also shows direct injections 710-717 of FIG. 7 have been replacedby port injections 715 a, 717 a, 711 a, and 713 a when estimates ofnoise levels are determined via knock windows associated withdeactivated cylinders or when crankshaft angular intervals where a knocksensor is sampled replace knock windows of deactivated cylinders. Byswitching to port fuel injection, noise from port injectors closing maybe characterized. Further, noise from direct injectors may be eliminatedto that engine knock background noise may be characterized withoutdirect injectors operating so that contributions of noise sources may bebetter characterized.

In these ways, contributions to a total engine knock background noiselevel may be determined. The contributions may be determined via knockwindows that are associated with the deactivated cylinder or viacrankshaft angular intervals (e.g., between crankshaft angle 90 degreesand crankshaft angle 140 degrees) may be determined without disturbingengine operation.

Referring now to FIG. 10, an example prophetic sequence that showsadvantages of modifying intake valve and fuel injection timing is shown.The timings and signals shown in FIG. 10 may be generated via the systemof FIGS. 1A-1C and the method of FIGS. 2-6. The double SS's locatedalong the horizontal axis of each plot represents a break in time thatmay be short or long in duration. Timings for two different enginecycles are shown to illustrate how actuator timing may affect engineknock background noise levels. Timings for a first engine cycle areshown left of the double SS marks and timings of a second engine cycleare shown right of the double SS marks.

The first plot from the top of FIG. 10 is a plot of knock window timingversus crankshaft angle. The vertical axis represents whether the knockwindow is open or closed. The knock window is open when trace 1002 is ata higher level near the vertical axis arrow. The knock window is closedwhen trace 1002 is at a lower level near the horizontal axis. Trace 1002represents a knock window of a cylinder. The crankshaft angle increasesfrom the left side of the figure to the right side of the plot.

The second plot from the top of FIG. 10 is a plot of knock sensor outputvoltage versus crankshaft angle. The vertical axis represents knocksensor voltage. Knock sensor output voltage increased in the directionof the vertical axis arrow. Knock intensity (not shown) increases asknock sensor output increases. Trace 1004 represents a knock sensoroutput voltage. The crankshaft angle increases from the left side of thefigure to the right side of the plot.

The third plot from the top of FIG. 10 is a plot of intake valve timingversus crankshaft angle. The vertical axis represents whether the intakevalve is open or closed. The intake valve is open when trace 1006 is ata higher level near the vertical axis arrow. The intake valve is closedwhen trace 1006 is at a lower level near the horizontal axis. Trace 1006represents a position of an intake valve of a cylinder. The crankshaftangle increases from the left side of the figure to the right side ofthe plot.

The fourth plot from the top of FIG. 10 is a plot of fuel injectortiming versus crankshaft angle. The vertical axis represents whether thefuel injector is open or closed. The fuel injector is open when trace1008 is at a higher level near the vertical axis arrow. The fuelinjector is closed when trace 1008 is at a lower level near thehorizontal axis. Trace 1008 represents a position of a fuel injector ofa cylinder. The crankshaft angle increases from the left side of thefigure to the right side of the plot.

Timings for the first engine cycle show that the intake valve closesnear top dead center compression stroke of the cylinder (e.g., zerocrankshaft degrees). The knock sensor responds to closing of the intakevalve by the knock sensor voltage increasing. Knock sensor outputreturns to a static level before the engine reaches five crankshaftdegrees. The knock window for the cylinder opens at five crankshaftdegrees and the noise caused by closing the intake valve is not capturedwithin the knock window. The fuel injector opens at fifteen crankshaftdegrees and the knock sensor output briefly increases. The noise of thefuel injector opening is fully captured within the cylinder knockwindow. The fuel injector closes at forty crankshaft degrees and theknock sensor output increases by a larger amount and for a longerduration. The noise of the fuel injector opening is not fully capturedwithin the cylinder knock window since the knock sensor indicates thatthe engine continues to vibrate after the knock window closes atforty-five crankshaft degrees.

Timings for the second engine cycle show that the fuel injector opens atten crankshaft degrees and closes at thirty-five crankshaft degrees. Inaddition, the intake valve closes at twenty-five crankshaft degrees.Thus, intake valve timing has been retarded and the fuel injector timinghas been advanced in the second engine cycle as compared to the firstengine cycle. The knock sensor responds to the opening of the fuelinjector and the closing of the intake valve, which is entirely withinthe span of the knock window. The knock sensor also responds to closingof the fuel injector and the knock sensor ceases responding to closingof the fuel injector before the knock window is closed. Consequently,the closing of the intake valve and opening and closing of the fuelinjector are fully captured within the knock window so that adetermination of an engine background noise level may include theopening and closing of the fuel injector in its entirety instead ofincluding just a portion of the fuel injector closing noise as shown inthe first sequence. The knock window closes at forty-five degrees afterthe knock sensor ceases to respond to the intake valve and fuel injectornoise.

Thus, by moving actuator timing, it may be possible to characterize afraction or a total amount of noise produced via a noise source duringseveral engine cycles. This may be beneficial to determine enginebackground noise levels for engines that include adjustable poppet valvetiming and adjustable fuel injection timing so that engine knockdetection may be improved via providing better estimates of engine knockbackground noise levels.

Note that the example control and estimation routines included hereincan be used with various engine and/or vehicle system configurations.The control methods and routines disclosed herein may be stored asexecutable instructions in non-transitory memory and may be carried outby the control system including the controller in combination with thevarious sensors, actuators, and other engine hardware. The specificroutines described herein may represent one or more of any number ofprocessing strategies such as event-driven, interrupt-driven,multi-tasking, multi-threading, and the like. As such, various actions,operations, and/or functions illustrated may be performed in thesequence illustrated, in parallel, or in some cases omitted. Likewise,the order of processing is not necessarily required to achieve thefeatures and advantages of the example examples described herein, but isprovided for ease of illustration and description. One or more of theillustrated actions, operations and/or functions may be repeatedlyperformed depending on the particular strategy being used. Further, thedescribed actions, operations and/or functions may graphically representcode to be programmed into non-transitory memory of the computerreadable storage medium in the engine control system, where thedescribed actions are carried out by executing the instructions in asystem including the various engine hardware components in combinationwith the electronic controller.

It will be appreciated that the configurations and routines disclosedherein are exemplary in nature, and that these specific examples are notto be considered in a limiting sense, because numerous variations arepossible. For example, the above technology can be applied to V-6, I-4,I-6, V-12, opposed 4, and other engine types. The subject matter of thepresent disclosure includes all novel and non-obvious combinations andsub-combinations of the various systems and configurations, and otherfeatures, functions, and/or properties disclosed herein.

The following claims particularly point out certain combinations andsub-combinations regarded as novel and non-obvious. These claims mayrefer to “an” element or “a first” element or the equivalent thereof.Such claims should be understood to include incorporation of one or moresuch elements, neither requiring nor excluding two or more suchelements. Other combinations and sub-combinations of the disclosedfeatures, functions, elements, and/or properties may be claimed throughamendment of the present claims or through presentation of new claims inthis or a related application. Such claims, whether broader, narrower,equal, or different in scope to the original claims, also are regardedas included within the subject matter of the present disclosure.

The invention claimed is:
 1. An engine operating method, comprising:ceasing to supply fuel to a first engine cylinder via a controller;reducing a crankshaft duration of a knock window of the first enginecylinder from a first duration when the knock window is applied toevaluate the presence of knock in a cylinder to a second duration whenthe knock window is applied to quantify an engine knock background noiselevel; sampling output of a knock sensor during the knock window via thecontroller; and generating the engine knock background noise level viasampling output of the knock sensor and learning propagation time ofnoise and noise duration.
 2. The method of claim 1, further comprisinggenerating an indication of engine knock via the engine knock backgroundnoise level.
 3. The method of claim 1, further comprising adjusting acrankshaft angle where the knock window opens.
 4. The method of claim 3,further comprising adjusting a crankshaft angle where the knock windowcloses.
 5. An engine operating method, comprising: adjusting timing ofan engine actuator via a controller to increase or decrease engine noisegenerated during a knock window associated with cylinder in response toa request to learn an engine knock background noise level; samplingoutput of a knock sensor during the knock window via controller; andceasing to supply fuel to one or more cylinders before and while timingof the device is adjusted, where the knock window is a knock windowassociated with a deactivated cylinder.
 6. The method of claim 5, whereadjusting timing of the engine actuator includes advancing timing of theengine actuator relative to a crankshaft position.
 7. The method ofclaim 5, where adjusting timing of the engine actuator includesretarding timing of the engine actuator relative to a crankshaftposition.
 8. The method of claim 5, where the engine actuator is a fuelinjector or a poppet valve.
 9. The method of claim 5, further comprisingsampling a first knock sensor during the knock window associated withthe cylinder before the request to learn the engine knock backgroundnoise level and sampling a second knock sensor during the knock windowassociated with the cylinder in response to the request to learn theengine knock background noise level.